4000 DPI is definitely not too much. I'm running the lachesis, and I'm a bit disappointed it doesn't go to 5000 DPI lol. I'm so used to 4000 I feel I could handle faster.
I've owned both the G15, and now the lycosa, and my personal experience with the lycosa is much more positive than the G15. That's not to say the G15 is a bad keyboard, it isn't. I just think The lycosa is one step ahead. They keys have great response and a nice feel to them, and the programming utility is a piece of cake. On the other hand, I never liked the feel of the G15's keys much.
The LCD is virtually useless. It was useful for the first couple weeks that I built my PC because I could display temps and info while overclocking and all that, but after you get everything overclocked and stable, there's no need to bother :/
As far as the info it displays for any games.. It isn't very useful. 9 out of 10 times, the info itself is already displayed on screen in some form or another, and while you're fighting or whatever, you don't really want to be looking away from the screen at the small LCD on the keyboard anyway.
All that being said, there is a really handy winamp application for it that can show all the track and artist info, as well as little visualizations. That's about it.
Anyway +1 for Razer products. The G15 is a good keyboard, but I like the lycosa more
I don't think I'll ever use a non razer mouse again. Unless something better is released of course, but IMHO there isn't anything yet.